An inverted power and free conveyor typically consists of a power track guiding power trolleys supporting a continuously driven power chain, a load track guiding load trolleys, and a load connected to the load trolleys and supporting loads to be conveyed. Each load trolley has a retractable load dog which is selectively engaged with one of a plurality of power dogs spaced along the power chain for powered movement of a load on a load trolley. Alternatively, the load dog can be retracted to brake a load carrier or for manually positioning the carrier. Inverted power and free conveyors find wide application in manufacturing industries, such as automotive assembly lines and the like.
Such conveyors are often installed with at least some sections having their components mounted below a floor level with only the load carrier and connection members or posts connected to corresponding load trolleys extending above the floor level through a long narrow opening or slot in the floor. In order to reduce contamination of the conveyor components from dust and other foreign matter, it is a common practice to close the floor slot with a longitudinally split resilient seal. As a load carrier moves along such a submerged conveyor section, the connection members, also referred to as seal separator pins, open the seal which then closes behind the connection members, somewhat in the manner of a zipper.
A problem with such split seals occurs at a junction of a main line or track of the conveyor with a branch or spur line. At a junction of a submerged inverted power and free conveyor, a slot for the branch line diverges from the main slot. One of the split seal members of the main line continues along an outer side of the main line, relative to the junction, while the other follows the branch line and becomes an outer seal member therefor. A new inner main seal member begins at the junction, as does an inner branch seal member. The problem arises as a result of the greater span across the area where the branch slot diverges from the main slot.
While it would be possible to extend portions of the inner branch and main seal members to cover the area of divergence of the slots, practical considerations rule out this solution. Such extended seal portions, or even a specially configured junction seal member, would be pointed in a direction counter to oncoming carrier connection members, the point being positioned on the centerline interface between the seal members of the main line. As a result, such pointed seal extensions or special seal member would quickly be damaged by the connection members. Additionally, the seal members must be resilient enough to allow splitting by the carrier connection members travelling therealong but stiff enough to prevent penetration by a worker walking over the seals or rolling the wheels of a cart, for example, thereover. This is easy enough to accomplish along the principal sections of the conveyor lines. However, in the divergence area at a junction, the increased span across the area of divergence and seals covering same would probably result in a "soft" spot, through which a workers foot or cart wheel might penetrate. This could result in serious injury to a worker or damage to a cart and/or a load being carried by the conveyor.
To avoid these problems, it is a common practice to leave the area of divergence of the slots open and to mark an area on the floor surrounding the seal gap with a highly visible warning in addition to verbally warning the workers as part of plant safety training. Despite such precautions, the existence of such a hazardous condition in a plant is likely to be disfavored by government industrial safety agencies and insurers of the plant, since an inattentive worker looking in the wrong direction while walking in the area of the seal gap might easily wedge a foot in the gap, with serious consequences.
What is needed is a mechanism which normally covers or closes the gap in the seal arrangement to prevent worker penetration and which does not interfere with the normal operation of the conveyor system.